My android login app unfortunately stopped

Question

My simple app getting unfortunately stopped error.
Kindly solve, please.

I do not need any permissions

Here is my android main activity:

package vk.com.login_simple;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.*;


public class MainActivity extends AppCompatActivity {
private EditText username=(EditText) findViewById(R.id.username);
private EditText password=(EditText) findViewById(R.id.password);
private Button login=(Button) findViewById(R.id.login);
private Button reset=(Button) findViewById(R.id.reset);
private Button exit=(Button) findViewById(R.id.exit);
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Login App");
        setContentView(R.layout.activity_main);

    }
    public void login(View view){
if(username.getText().toString().equals("admin")&&password.getText().toString().equals("password")){
    Toast.makeText(getApplicationContext(),"Login Success",Toast.LENGTH_LONG).show();
//your code here
}else{
    Toast.makeText(getApplicationContext(),"Wrong Username / Password",Toast.LENGTH_LONG).show();
}
    }

    public void reset(View view) {
        username.setText("");
        password.setText("");
        Toast.makeText(this,"Reset success",Toast.LENGTH_LONG).show();
    }
    public void exit(){
        //empty
    }
}

https://vivekp.co/activity_main.xml https://vivekp.co/n.txt For logcat — Vicky, Nov 23 '17 at 03:29

nhoxbypass · Accepted Answer · 2017-11-23T03:19:57.500

findViewById ONLY work after you setContentView() which define the root view of your layout, to show where the Views can be found. If you call it outside Android don't know how and where to find Views for you.

So what you MUST do is place all of the findViewById() code inside onCreate() and after setContentView().

private EditText username;
private EditText password;
private Button login;
private Button reset;
private Button exit;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        setTitle("Login App");

        username=(EditText) findViewById(R.id.username);
        password=(EditText) findViewById(R.id.password);
        login=(Button) findViewById(R.id.login);
        reset=(Button) findViewById(R.id.reset);
        exit=(Button) findViewById(R.id.exit);

    }

score 0 · Answer 2 · answered Nov 23 '17 at 03:09

package vk.com.login_simple;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.*;


public class MainActivity extends AppCompatActivity {
private EditText username;
private EditText password;
private Button login;
private Button reset;
private Button exit;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        username=(EditText) findViewById(R.id.username);
        password=(EditText) findViewById(R.id.password);
        login=(Button) findViewById(R.id.login);
        reset=(Button) findViewById(R.id.reset);
        exit=(Button) findViewById(R.id.exit);
        setTitle("Login App");


    }
    public void login(View view){
if(username.getText().toString().equals("admin")&&password.getText().toString().equals("password")){
    Toast.makeText(getApplicationContext(),"Login Success",Toast.LENGTH_LONG).show();
//your code here
}else{
    Toast.makeText(getApplicationContext(),"Wrong Username / Password",Toast.LENGTH_LONG).show();
}
    }

    public void reset(View view) {
        username.setText("");
        password.setText("");
        Toast.makeText(this,"Reset success",Toast.LENGTH_LONG).show();
    }
    public void exit(){
        //empty
    }
}

You can use findViewById after they have been created in your onCreate() method.

score 0 · Answer 3 · answered Nov 23 '17 at 03:09

Put your parsing inside onCreate() method

 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    username=(EditText) findViewById(R.id.username);
    password=(EditText) findViewById(R.id.password);
    login=(Button) findViewById(R.id.login);
    reset=(Button) findViewById(R.id.reset);
    exit=(Button) findViewById(R.id.exit);
}

score 0 · Answer 4 · answered Nov 23 '17 at 03:17

parse inside onCreate method

public class MainActivity extends AppCompatActivity {
private EditText username;
private EditText password;
private Button login;
private Button reset;
private Button exit;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Login App");
        setContentView(R.layout.activity_main);
        username=(EditText) findViewById(R.id.username);
        password=(EditText) findViewById(R.id.password);
        login=(Button) findViewById(R.id.login);
        reset=(Button) findViewById(R.id.reset);
        exit=(Button) findViewById(R.id.exit);
    }
}

instead of parsing use butterknife

public class MainActivity extends AppCompatActivity {
    @BindView(R.id.username)
    private EditText username;
    @BindView(R.id.password)
    private EditText password;
    @BindView(R.id.login)
    private Button login;
    @BindView(R.id.reset)
    private Button reset;
    @BindView(R.id.exit)
    private Button exit;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setTitle("Login App");
        setContentView(R.layout.activity_main);
    }
}

score 0 · Answer 5 · answered Nov 23 '17 at 03:19

You have to initialize inside onCreate method like belllow

  @Override
protected void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);       
     setContentView(R.layout.activity_main);

     EditText username=(EditText) findViewById(R.id.username);
     EditText password=(EditText) findViewById(R.id.password);
     Button login=(Button) findViewById(R.id.login);
     Button reset=(Button) findViewById(R.id.reset);
     Button exit=(Button) findViewById(R.id.exit);


}

My android login app unfortunately stopped

5 Answers5